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SoldierTech: Stealth Ships

NOT YOUR GRANDPA'S SHOOTIN' IRON: Rail Guns

 

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[Have opinions on this article or equipment? Go to the Discussion Forum to sound off.]

  Rail Gun
The Big Bang: An experimental rail gun, with loads of firepower (Photo courtesy of Sam Barros' Powerlabs).

Rail Gun: Hot Facts

A projected naval rail gun with a 2.5km/sec muzzle velocity could deliver a guided projectile with an impact velocity of Mach 5 to targets at ranges of 250 miles, at a rate greater than 6 rounds per minute.

A test demonstrated that a rail gun projectile's kinetic energy could create a 10-foot diameter crater, 10 feet deep in solid ground, and achieve projectile penetration to 40 feet - 3 to 5 times more effective than current guns.

Rail gun projectiles are smaller and easier to store: a standard AGS magazine holds 1,500 rounds; a rail gun magazine could hold 10,000 rounds in the same amount of space.

Source: Batelle

A gun that accelerates a bullet to a speed of 13,000 miles per hour in 0.2 seconds? Seems like a science fiction dream, but don't even blink -- with advances in rail gun technology, a new era of high-speed military weaponry is coming right at us, faster than a speeding bullet.

In the "more things change, the more they stay the same" category, we give you basic gun physics. Despite numerous advancements over the last millennium, all guns, from the blunderbuss to the M-16, have operated on the "expanding gas" principle, where an expanding ball of superheated gas is used to force a projectile through a tube.

Well, no longer. Gunpowder, as we know it, may soon become a thing of the past. Make way for the rail gun, a device that substitutes electromagnetic (EM) propulsion for gunpowder, with devastating results in speed and kinetic power. Arnold Schwarzenegger (who took out the baddies with a similar device in the movie "Eraser") would approve.

Zero to 13,000 MPH in 0.2 Seconds

An EM projector (i.e. rail gun) uses electrical energy to accelerate projectiles to extreme velocities. How fast? Tests conducted at the University of Canberra were able to accelerate a 16-gram projectile down a 5 meter barrel at 250,000 gravities, for a muzzle velocity of 5,900 meters per second. Loosely translated, that's an acceleration from 0 to 13,000 miles per hour in the span of 0.2 seconds, not bad even for Superman. This also translates to an enormous amount of kinetic energy, at a fraction of the mass needed for a normal bullet. A quick comparison: an anti-armor projectile shot from a rail gun at 3,000 m/sec (almost twice the speed of current kinetic energy penetrators) would only need to be roughly one-fifth of the mass of a standard projectile to deliver the same amount of destructive force. Electromagnetic-power also has the advantage of stealth: Reduced logistics (rounds can have a smaller weight and volume), and the lack of chemical propellant means it will be difficult for opponents to track.

  Rail Gun Schematic
The Principle: A diagram of the rail gun's critical parts.

How are these impressive speeds reached? A rail gun is essentially two parallel conductive metal plates through which an electrical current is passed. This electrical current creates opposed linear magnetic fields along the axis of the rails. The projectile itself is placed between the rails, and a "driver" (armature) is placed behind the projectile. The function of the armature is to close the circuit between the two rails. When the rails are energized, a third magnetic field is created in the armature which is repulsed by the fields created in the rails, thus "driving" it down the barrel. The energy required to drive projectiles at useful velocities is enormous; peak power outputs are measured in millions of amperes.

Naval Know-How

  Rail Gun Sketch
Logical choice: The Navy's DD(X) destroyer, currently under construction, could be ideally suited to carry an electromagnetic rail gun (Lockheed Martin photo).

Obviously, it would be fitting for a weapon with such potential power to be housed in the most powerful vessel around. The Navy, which has been at the forefront of rail gun technology since the early 1980s, plans to incorporate rail gun technology with its next-generation surface fleet, which will include ships such as the hefty DD(X) destroyer. Ranges of up to 200 nautical miles for rail gun projectiles are envisioned, with GPS-guided projectiles traveling at six times the speed of sound. The fact that rail guns and directed-energy weapons do not require powders or explosives will free magazine space for strike and other mission areas (the trade-off is that surface ships will need to generate massive amounts of electric power to support them). A proper-sized round could provide missile-like capability. Take your standard Tomahawk land-attack cruise missile -- for the same amount of time it takes a Tomahawk to reach a target, an EM gun can deliver twice the destructive power to the same target, while operating at about 6-12 rounds per minute. At a fraction of the cost per round, tremendous volume fires could be delivered. The DD(X) destroyer, with its all-electric drive and Integrated Power System (IPS), is the first step towards full electromagentic weapon capability. The IPS can scale up to provide additional electrical power as demand grows -- the key to surface fire support capabilities.

Beans and Bullets: Other EM Applications in Combat and Logistics

The Navy has grabbed the most press with its rail gun experiments but the Army Research Laboratory (ARL) and Lockheed Martin are developing an Electromagnetic (EM) Gun System in a two-phase program. The first phase (scheduled to conclude in 2005) is centered on a medium caliber gun demonstration, and demonstrating a single rotating power supply. During Phase II (2005-2007), EM technologies will be integrated into an armament test-bed, utilizing a large bore gun.

  Rail Gun Sketch
On the drawing board: A sketch of a next-generation Army vehicle equipped with an EM gun (Lockheed Martin photo).

Fired at hyper velocities (10-100 kilometers/second), projectiles weighing a fraction of a gram have enormous destructive potential, and could be fired using the stored energy of a standard armored vehicle power plant. In addition to combat (especially anti-armor and hard target applications), EM research is also looking into using rail gun technology to deliver supplies over long distances. Launched from a 100m ramp, a 300-pound aerodynamic supply package could be "shot" over intervening terrain and remotely guided to a designated landing area. The concept is sound -- it only remains to develop the correct technology.

 
Related Links

Sam Barros' Powerlabs
EM gadgets aren't just for multi-million dollar military projects -- a student at Michigan Technological University has gained attention for his pioneering experiments with electromagnetic technology.

The Next Revolution at Sea
Rail guns are only part of the picture in the Navy's next-generation warfare plans. Get a peek at some of the vessels and weapons on the drawing table.

Continuing on the transportation theme, laboratories utilizing electromagnetic technology are already working on a Segmented Rail Phased Induction Motor (SERAPHIM), which opens the door for high-speed ground transportation systems (i.e., next-generation monorails). Similar linear induction motors are already being used for airport transit systems, subways, amusement park rides, and industrial handling systems.

Building It Was the Easy Part…

Although the principles behind rail gun technology have been well documented and understood for nearly 50 years now, challenges remain in building a reliable, effective, and efficient EM gun. When an electrical current is passed through non-super conductive material, a fraction of that current is converted to heat by the impedance of the conductive material. Given the huge amounts of energy involved (even when energized for only milliseconds), the heat generated by a rail gun would be enough to melt the gun's rails, if used often enough. If EM guns are going to serve as practical battlefield weapons, a means of cooling them (cryogenically or otherwise) or of improving the super-conductivity of the rails must be found.

One naval proposal has suggested using liquid nitrogen to cool the rails, with a seawater-based heat exchanger to cool the electrical storage and discharge systems. In addition, to function properly, the armature must make physical contact between the rails. This requirement creates some problems: If the current is too great and the armature has too little mass to absorb the resistant heat energy being transferred to it by the electric current, the armature may melt or weld itself to the rails.

Must-Have Gear


One method of reducing armature "welding" is to make the armature's rail contact surfaces (brushes) out of a light metal, such as aluminum, which will vaporize into plasma (ionized gas) when energized. This process, known as metal vapor arcing (MVA), eliminates physical contact between the rails while simultaneously closing the circuit (the metal plasma is conductive.) One of the drawbacks to MVA is the buildup of metallic residue on the rails, which is formed when the metal vapor cools inside the barrel. In the same vein, if the rails are placed too close together, the current between the rails may bypass the armature (arc) and damage the rails. Given the velocity at which the armature is driven down the barrel, this friction could further add to heat build-up, and degrade the driver as it moves down the barrel.

Finally, since the individual magnetic fields created in the rails are repulsed by one another, a tremendous strain is placed on the rails as they try to push away from one another. While rail guns do not suffer from the traditional recoil forces associated with conventional expanding gas weapons, this repulsive effect can be equally destructive if not properly compensated for.

The challenges facing the development of rail guns as a practical, widespread weapon are hefty, but as better super conductive materials are researched, they come closer and closer to becoming a reality. And with the speeds that EM power can provide, you can try running, but you sure can't hide.

[Have opinions on this article or equipment? Go to the Discussion Forum to sound off.]


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